Yup, teamed up a few times with guild members. On the TWC side, I've been teaming up with Jasra regurarly for Heroics or whatever quests we still had to do on a planet. That has been fun. On the IMB side, I've not really had to have much help, my Merc can do most things by himself. Still, have done some dailies with DarthParametric and Lynk.
Also, during the first days of launch, when the IMB guild only had about 4 members, I ran into Astor a few times randomly. Always fun.
Anyway, my Guardian's still a bit helpless himself, but if anyone needs help on the IMB side, whether it's questing, flashpoints or you want some armor crafted, my Merc's available for help, mostly on weekends.